Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.13 (protein kinase C)
 49,245 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Recent studies have demonstrated that phorbol diesters enhance the release of various neurotransmitters. It is generally accepted that activation of protein kinase C (PKC) is the mechanism by which phorbol diesters act on neurotransmitter release. The action of PKC in neurotransmitter release is very likely mediated by phosphorylation of substrate proteins localized in the presynaptic nerve terminal. An important presynaptic substrate of PKC is B-50. To investigate whether B-50 mediates the actions of PKC in neurotransmitter release, we have studied B-50 phosphorylation in intact rat hippocampal slices under conditions that stimulate or inhibit PKC and neurotransmitter release. The slices were labelled with [32P]orthophosphate. After treatment, the slices were homogenized, B-50 was immunoprecipitated from the slice homogenate, and the incorporation of 32P into B-50 was determined. Chemical depolarization (30 mM K+) and the presence of phorbol diesters, conditions that stimulate neurotransmitter release, separately and in combination, also enhance B-50 phosphorylation. Polymyxin B, an inhibitor of PKC and neurotransmitter release, decreases concentration dependently the depolarization-induced stimulation of B-50 phosphorylation. The effects of depolarization are not detectable at low extracellular Ca2+ concentrations. It is concluded that in rat hippocampal slices B-50 may mediate the action of PKC in neurotransmitter release.
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PMID:Phosphorylation of B-50 (GAP43) is correlated with neurotransmitter release in rat hippocampal slices. 256 6

The neuron-specific, growth-associated protein B-50, also known as GAP-43. F1 and neuromodulin, shows a striking heterogeneous behaviour in many chromatographic and electrophoretic systems. A modulatory function has been proposed for the protein in receptor-mediated processes in the presynaptic membrane. Fatty acid acylation, calmodulin binding and phosphorylation appear to be tools in this respect. At least three discrete isoforms were present in separations made by reversed-phase fast protein liquid chromatography (FPLC) of the phosphorylated protein. In anion-exchange FPLC chromatography a conglomerate of eight peaks was eluted, which migrated as eight parallel curves in electrophoretic mobility studies. After dephosphorylation of the protein this number was reduced to two. Under non-reducing conditions, the phosphoprotein was eluted from an FPLC gel filtration column at Mr = 270 kDa, i.e. 8-12 times the size of the monomer (m = 23.6 kDa.) In sodium dodecyl sulphate polyacrylamide gel electrophoresis all isoforms showed only B-50 at Mr of 48 kDa and its breakdown product (Mr = 40 kDa) in a constant ratio. It was concluded that phosphorylation by protein kinase C of a single serine residue is only one factor in the microheterogeneity of B-50. Multimeric forms may also add to the heterogeneous behaviour of phosphorylated B-50.
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PMID:Microheterogeneity of the growth-associated neuronal protein B-50 (GAP-43). Contribution of phosphorylation by protein kinase Ca. 262 38

The neuronal protein B-50 may be involved in diverse functions including neural development, axonal regeneration, neural plasticity, and synaptic transmission. The rat B-50 sequence contains 226 amino acids which include 14 Ser and 14 Thr residues, all putative sites for phosphorylation by calcium/phospholipid-dependent protein kinase C (PKC). Phosphorylation of the protein appears to be a major factor in its biochemical and possibly its physiological activity. Therefore, we investigated rat B-50 phosphorylation and identified a single phosphorylated site at Ser41. Phosphoamino acid analysis eliminated the 14 Thr residues because only [32P]Ser was detected in an acid hydrolysate of [32P]B-50. Staphylococcus aureus protease peptide mapping produced a variety of radiolabelled [32P]B-50 products, none of which had the same molecular weights or HPLC retention times as several previously characterized fragments. Indirect confirmation of the results was provided by differential phosphorylation of major and minor forms of B-60 that have their N-termini at, or C-terminal to, the Ser41 residue and are the major products of specific B-50 proteolysis. Only those forms of B-60 that contained the Ser41 residue incorporated phosphate label. The results are discussed with reference to the substrate requirements for B-50 phosphorylation by PKC and the proposed structure of the B-50 calmodulin binding domain.
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PMID:Evidence for a single protein kinase C-mediated phosphorylation site in rat brain protein B-50. 280

Accumulating evidence indicates that the neuron-specific B-50/GAP43, a substrate for protein kinase C, plays a role in neuronal differentiation and neuritogenesis during nervous tissue development and axonal regeneration. An ultrastructural immunocytochemical study on the localization of B-50 in presynaptic terminals (synaptosomes) isolated from the frontal cortex of 6-week-old rats, and in neuronal growth cones, isolated from forebrains of 5-day-old rats, the majority of B-50 is detected at the surrounding neuronal plasma membrane. In both neuronal growth cones and synaptosomes, a relatively small fraction of B-50 in the cytoplasm was not evidently associated with internal membranes. Our results indicate that B-50 is mainly located at the cytoplasmic face of the synaptosomal and neuronal growth cone plasma membrane. The similar B-50 localization in neuronal growth cones and synaptosomes suggests that, both in extending axons and mature synaptic terminals, B-50 may exert identical functions as a protein kinase C substrate at the plasma membrane.
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PMID:Ultrastructural immunocytochemical localization of B-50/GAP43, a protein kinase C substrate, in isolated presynaptic nerve terminals and neuronal growth cones. 280 34

The neuron-specific phosphoprotein B-50 (Mr 48 kDa, isoelectric point, IEP, 4.5), which is identical to GAP43, is a member of a family of growth-associated proteins. Protein B-50 is a major phosphoprotein in nerve growth cones isolated from fetal rat brain. In a growth cone particulate fraction (GCp), endogenous B-50 phosphorylation is Ca2+-dependent and is unaffected by cAMP. Addition of purified protein kinase C (PKC) to GCP enhances B-50 phosphorylation. In heat-inactivated GCp, B-50 is one of the major substrates of purified PKC. Endogenous B-50 phosphorylation in GCP is stimulated in a dose-dependent manner by 4 beta-phorbol diesters, known to activate PKC, but not by the inactive 4 alpha-phorbol derivatives. In synaptic plasma membranes (SPM) isolated from adult rat brain, the degree of B-50 phosphorylation has been implicated in the modulation of receptor-mediated polyphosphoinositide (PPI) hydrolysis. In addition to B-50 and its kinase, PKC, the GCp fraction was also shown to contain all other components of such a modulatory system: the phosphatidylinositol 4-phosphate (PIP)-kinase, as shown on Western blots with affinity-purified IgGs against PIP-kinase, and the polyphosphoinosides, PIP and phosphatidylinositol 4,5-bisphosphate (PIP2), since the addition of gamma-32P-ATP to the GCp fraction not only results in B-50 phosphorylation but also in the labeling of phosphatidic acid (PA), PIP, and PIP2. ACTH1-24, which inhibits B-50 phosphorylation in the GCp fraction in a dose-dependent manner (IC50 = 5 x 10(-6) M), stimulates PIP2 labeling dose-dependently in the same preparation.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:B-50 phosphorylation and polyphosphoinositide metabolism in nerve growth cone membranes. 283 51

One of the major phosphoproteins in synaptic plasma membranes (SPM) is the neuron-specific protein B-50 (Mr 48 kDa, IEP 4.5). Addition of purified protein kinase C (PKC) to native SPM increases B-50 phosphorylation. Exogenous PKC also phosphorylates B-50 in heat-inactivated SPM. Endogenous phosphorylation of B-50 in SPM is enhanced in a concentration-dependent manner by the tumor-promoting phorbol diesters 4 beta-phorbol 12-myristate, 13-acetate, 4 beta-phorbol 12,13-dibutyrate (PDB) and 4 beta-phorbol 12,13-diacetate, with an EC50 of 7 x 10(-8) M, 3 x 10(-7) M and 10(-6) M, respectively. This increase in the B-50 phosphorylation can be inhibited by ACTH1-24. PDB (10(-6) M) also stimulates B-50 phosphorylation by exogenous PKC in native and heat-inactivated SPM (204 and 712%, respectively). The increase in B-50 phosphorylation induced by the addition of PKC to SPM is accompanied by a decrease in the [32P]-incorporation into phosphatidylinositol 4,5-bisphosphate (PIP2). These data support the hypothesis that in neuronal membranes the degree of B-50 phosphorylation exerts a negative control on receptor-mediated hydrolysis of PIP2 in receptor systems coupled to phospholipase C.
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PMID:Modulation of B-50 phosphorylation and polyphosphoinositide metabolism in synaptic plasma membranes by protein kinase C, phorbol diesters and ACTH. 283 21

Intraventricular administration of ACTH1-24 induces excessive grooming in the rat. Ethogram analysis shows that the peptide does not alter grooming behavior seen in a novel box, but that it prolongs the duration of the grooming bout. Extensive structure-activity studies have been performed which suggest that the active site lies in a region (5-13) of the ACTH molecule. Interestingly, the (1-24) sequence is fully active, whereas (1-10) and (11-24) alone or in combination are inactive, pointing to a specific stereoconformation necessary to induce grooming. However, despite the fact that there are ACTH-and/or alpha-MSH-containing peptidergic neurons, no conclusive evidence is available demonstrating stereospecific, saturable binding sites for these peptides in brain. The analysis of the neural substrate underlying ACTH-induced excessive grooming has been performed by means of electrolytic lesions of specific brain regions and by neuropharmacological manipulations. The data suggest that the periaqueductal gray is the primary target for ACTH and that the activity of neostriatum and accumbens, via a nigro-colliculus-periaqueductal gray pathway, modulates the display of excessive grooming. An important feature of the neural substrate is that it displays single-dose tolerance to the peptide during the first hours after the first peptide injection. It is suggested that the tolerance is a feature of an opioid receptor-containing component of the neural substrate. The molecular mechanism of action of ACTH is complex and may involve different transmembrane signal transduction systems. The peptide decreases the degree of phosphorylation of a neuron-specific, synaptic phosphoprotein B-50 by inhibition of protein kinase C. It is concluded that changes in the degree of phosphorylation of B-50 regulate the activity of the lipid kinase phosphatidylinositol 4-phosphate kinase. Therefore, the B-50 protein seems to be part of a negative feedback loop in the receptor-activated hydrolysis of phosphatidylinositol 4,5-bis-phosphate (PIP2). There is increasing evidence that the molecular mechanism by which ACTH brings about the grooming response involves a change in phosphorylation of B-50. Firstly, the structure-activity relationship of ACTH-induced excessive grooming is nearly identical to that obtained for ACTH-induced inhibition of protein kinase C.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Molecular transduction mechanisms in ACTH-induced grooming. 283 22

The presynaptic, nervous tissue-specific phosphoprotein B-50 is present in infant and adult rat brain. In the present study we demonstrate that B-50 is a major phosphoprotein in nerve growth cones obtained from fetal rat brain. As this protein is an endogenous substrate for protein kinase C, an enzyme linked to cell growth and proliferation, a role for B-50 in nerve growth cone function is suggested.
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PMID:Phosphoprotein B-50 in nerve growth cones from fetal rat brain. 293 47

A radioimmunoassay (RIA) for the B-50 protein was developed to determine B-50 in total homogenates of rat tissues. A tracer of purified B-50 was prepared at high activity (10-30 microCi/micrograms protein) by phosphorylating B-50 with carrier-free [gamma-32P]ATP, catalyzed by purified protein kinase C. The RIA was performed using affinity-purified anti-B-50 immunoglobulins G in a detergent containing medium and detected B-50 at levels of 0.1-10 ng. Specificity of the antibodies was ascertained by immunoprecipitation of B-50 from a crude mitochondrial membrane fraction from rat brain and by immunoblotting. For the B-50 content in rat brain the following distribution pattern was found: medulla spinalis less than cerebellum less than hippocampus; cerebral cortex less than periaqueductal gray less than septum. The septum contained 80 micrograms/g tissue weight. The level in liver homogenates was below detection. The regional distribution is in fair agreement with the pattern of the endogenous B-50 phosphorylation in rat brain synaptosomal plasma membranes previously reported.
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PMID:A radioimmunoassay for the phosphoprotein B-50: distribution in rat brain. 293 82

The short chain diacylglycerol, 1,2-dioctanoylglycerol, at concentrations of 100-300 microM stimulated phosphorylation of the nervous system-specific membrane protein B-50 (Mr 48 kDa, IEP 4.5) in isolated synaptic plasma membranes both in the presence and absence of exogenous protein kinase C. Comparable enhancement of histone phosphorylation by purified protein kinase C was achieved with 1 microM neutral lipid. Phorbol dibutyrate was 100 times more potent than the diacylglycerol in stimulating endogenous B-50 kinase in the membranes, whereas 4-alpha-phorbol was without effect. These results further confirm that B-50 is phosphorylated physiologically by a C kinase. Our data are consistent with a negative feedback mechanism in which generation of 1,2-diacylglycerol by enhanced phosphatidylinositol-4,5-bisphosphate hydrolysis could stimulate B-50 phosphorylation, thereby diminishing phosphatidylinositol-4-phosphate kinase activity and decreasing phosphatidylinositol-4,5-bisphosphate biosynthesis.
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PMID:Dioctanoylglycerol and phorbol diesters enhance phosphorylation of phosphoprotein B-50 in native synaptic plasma membranes. 294 Oct 12


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